The Night Sky

Why we love it

Though we often think of GIS as focused on the earth, ArcGIS Pro is powerful enough to map the heavens above. We love how this star chart and companion story map use vivid illustrations and clear explanations for celestial mapping terms such as coordinates and constellation boundaries. The charts make great use of color and labels, and the map offers a beautiful depiction of the arc of the Milky Way across the sky. Minimal constellation figures in the overview maps help us to quickly orient ourselves in the night sky.

Why it works

This map presents the endeavor of charting the stars as an approachable map-making process, using clever cartographic techniques for visualisation. The graduated symbology represents the stars’ relative brightness. This gives the chart depth atop intuitive nighttime colors. Larger areas of the night sky are made prominent by a smart labeling hierarchy, while annotation further enhances the labels. A clean layout brings together Northern and Southern hemisphere charts. Each technique makes this very dense dataset beautifully legible.

Important steps

See exactly how the author created this map

The map author of “The Night Sky” created a companion story map tutorial. This step-by-step guide walks you through how to build this map using ArcGIS Pro.

Use declination and right ascension coordinates

Instead of latitude and longitude coordinates, star charts use declination and right ascension. In ArcGIS Pro, you can make a spatial layer of your star chart table by making an XY Event Layer and setting the Declination as the Y field.

Make a map for each hemisphere

Divide the Northern and Southern hemispheres into their own views, and rotate the Southern hemisphere by 180 degrees This will allow you to display the Milky Way as a continuous feature across both views.

Analysis

The chart required manipulation of data and graphics. For example, the author used georeferencing and custom projections to create the Milky Way polygons, and the Feature Outline Masks tool for annotation masking.

Time

Using the provided data, and without agonising over any design considerations, you could recreate this map in 1 to 2 days. Most of the work is in placing and editing text. It originally took about 4 months of experimentation to arrive at this final map.

Tips and tricks

Polar Stereographic projection provides great results.

Use separate views for the Northern and Southern hemispheres, rotating the Southern 180°.